Recently, a light emitting diode (LED) is spotlighted as a light emitting device. Since the LED can convert electric energy into light energy with high efficiency and long life span of about 5 years or more, the LED can remarkably reduce the energy consumption and repair and maintenance cost. In this regard, the LED is spotlighted in the next-generation lighting field.
Such an LED includes a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer, in which the active layer generates light according to current applied thereto through the first and second conductive semiconductor layers.
The LED may be classified into a lateral type LED and a vertical type LED.
According to the lateral type LED, a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer are formed on a growth substrate, and the second conductive semiconductor layer, the active layer and the first conductive semiconductor layer are partially removed such that a part of the first conductive semiconductor layer can be exposed to form an electrode layer. Thus, the light emitting area may be reduced so that the light efficiency may be degraded.
In addition, according to the lateral type LED, since the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer are formed on the growth substrate having low thermal conductivity, the heat dissipation is not easy.
In contrast, according to the vertical type LED, a first electrode layer is formed on the first conductive semiconductor layer and a second electrode layer is formed under the second conductive semiconductor layer, so it is not necessary to remove the active layer to form the electrode layer. Thus, the light emitting area may not be reduced, so that the light efficiency may be improved as compared with that of the lateral type LED.
In addition, according to the vertical type LED, heat is transferred through the second electrode layer, so the heat dissipation is easy.
Meanwhile, the vertical type LED may employ the electroplating scheme and the wafer bonding scheme when the second electrode serving as a support substrate is formed under the second conductive semiconductor layer.
If the support substrate is manufactured through the electroplating scheme, the manufacturing process may be facilitated, but the reliability of the LED may be degraded. In addition, if the support substrate is manufactured through the wafer bonding scheme, the manufacturing process may be complicated, but the reliability of the LED may be improved.
In particular, if the support substrate is manufactured through the wafer bonding scheme, since the growth substrate and the support substrate are made from heterogeneous materials, the crack or debonding may occur in the LED after the wafer has been bonded due to thermal stress caused by difference in thermal expansion coefficient.